Miller said the number of peanut allergy incidents has tripled in the past decade.

"It's a tough question to answer why," Miller said. "But there are some theories, including that we dry roast peanuts in this country, versus boiling them like much of the rest of the world. The theory is that may create a more allergenic peanut."

Miller said immunotherapy, involving the use of peanuts to build a tolerance with affected persons, has shown some success, but remains controversial within the medical profession.

As for Brothers, who witnessed the girl's death, he said what he saw is proof no one should ever scoff when confronted with a separate peanut-free table in the school cafeteria or a request not to eat peanuts on an airplane.

"There were people who rolled their eyes, I'm sure, but no one ever said anything. I'm sure no one will ever do that again, because we now know what one bite of a peanut can do to a young girl," Brothers said.

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Diplomats and negotiators kept working Tuesday as a deadline approached to reach a deal on a framework agreement on Iran's nuclear program, but a U.S. State Department official said the discussion may continue after the cutoff.